The conventional straight-handled toothbrush renders it difficult to apply the bristles in the correct orientation on all the teeth in both the upper and lower jaws on both sides of the mouth. In the past, various toothbrush handle designs have been proposed which incorporated some form of bend or angle, which was intended to give easier access to certain of the teeth. Usually however, these modifications resulted in making access to other teeth in other locations still more difficult than before.
One attempt to overcome the problem with accessibility has been to provide a knuckle joint, or swivel connection in the brush handle, so that the toothbrush head could be bent into various different angular positions relative to the handle. However, this is not a satisfactory solution to the problem, since in order to be effective the brush head would have to be locked firmly at the swivel joint and its position changed for each surface addressed. While a muscular person might find this relatively easy, a child or an elderly or handicapped person would find it impossible.
Even this type of brush handle with a hinge or joint did not provide the best access to teeth in all positions in both upper and lower jaws. Access to some teeth is facilitated by a bend in the handle in one plane, while access to other teeth is improved by an axial semi-rotation or twist.
These combined features were not available in the earlier toothbrush designs referred to.